In the Linux kernel, the following vulnerability has been resolved:
iommufd: Avoid locking internal accesses during unmap
iommufd_access_notify_unmap() skips internal accesses because they do
not have an external unmap callback to invoke.
However, the current test calls iommufd_lock_obj() before checking
whether the access is internal. If iommufd_lock_obj() succeeds, the loop
then sees the internal access and continues, bypassing the matching
iommufd_put_object() used by the normal unmap path. This leaks the
object reference taken by iommufd_lock_obj().
Check for internal accesses first so skipped entries are never locked.
